U.S. patent application number 13/825718 was filed with the patent office on 2014-06-26 for machine type communications in a radio network.
This patent application is currently assigned to ALCATEL LUCENT. The applicant listed for this patent is Osman Aydin, Uwe Doetsch. Invention is credited to Osman Aydin, Uwe Doetsch.
Application Number | 20140177525 13/825718 |
Document ID | / |
Family ID | 44532802 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140177525 |
Kind Code |
A1 |
Aydin; Osman ; et
al. |
June 26, 2014 |
MACHINE TYPE COMMUNICATIONS IN A RADIO NETWORK
Abstract
The invention relates to a method for providing information from
a machine device, in particular from a sensor device (S1), to a
radio access network (RAN), comprising: transmitting, by the
machine device (S1), a plurality of Random Access Channel preambles
(P1 to P3) over a Random Access Channel, the information being
encoded by transmitting the Random Access Channel preambles (P1 to
P3) with frequency offsets (.DELTA.f) relative to each other. The
invention also relates to a machine device, in particular to a
sensor device (Sn), adapted to perform the encoding, and to a
receiving device for decoding the encoded information.
Inventors: |
Aydin; Osman; (Stuttgart,
DE) ; Doetsch; Uwe; (Freudental, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aydin; Osman
Doetsch; Uwe |
Stuttgart
Freudental |
|
DE
DE |
|
|
Assignee: |
ALCATEL LUCENT
Paris
FR
|
Family ID: |
44532802 |
Appl. No.: |
13/825718 |
Filed: |
July 22, 2011 |
PCT Filed: |
July 22, 2011 |
PCT NO: |
PCT/EP11/62648 |
371 Date: |
March 22, 2013 |
Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W 74/0866 20130101;
H04W 74/08 20130101; H04W 4/70 20180201; H04L 67/12 20130101; H04W
84/18 20130101 |
Class at
Publication: |
370/328 |
International
Class: |
H04W 4/00 20060101
H04W004/00 |
Claims
1. Method for providing information from a machine device, in
particular from a sensor device, to a radio access network,
comprising: transmitting, by the machine device, a plurality of
Random Access Channel preambles over a Random Access Channel,
wherein the information is encoded by transmitting the Random
Access Channel preambles with pre-selected frequency offsets
relative to each other.
2. Method according to claim 1, wherein the information is also
encoded by transmitting the Random Access Channel preambles with
pre-selected timing offsets relative to each other.
3. Method according to claim 1, wherein two or more of the Random
Access Channel preambles are transmitted at the same point of
time.
4. Method according to claim 1, wherein the information is also
encoded using the content of the Random Access Channel preambles,
in particular their sequence numbers.
5. Method according to claim 1, wherein at least one of the
frequency offsets, the timing offsets, and the content of the
Random Access Channel preambles is pre-configured in the machine
device upon installation of the machine device.
6. Method according to claim 1, wherein the encoded information
comprises identification information for identifying the machine
device and/or status information for informing the radio access
network about a status of the machine device.
7. Method according to claim 1, wherein the Random Access Channel
preambles are transmitted using a power level which is selected
based on a power level of a previous successful communication
between the machine device and the radio access network over the
Random Access Channel.
8. Machine device, in particular sensor device, comprising: a
transmission unit adapted for transmitting a plurality of Random
Access Channel preambles over a Random Access Channel to a radio
access network, and an encoding unit for encoding information to be
provided to the radio access network over the Random Access
Channel, wherein the encoding unit is adapted to encode the
information by selecting frequency offsets between the Random
Access Channel preambles to be transmitted by the transmission
unit.
9. Machine device according to claim 8, wherein the encoding unit
is further adapted to select timing offsets between the Random
Access Channel preambles for encoding the information.
10. Machine device according to claim 8, wherein the encoding unit
is further adapted to select the content of the Random Access
Channel preambles, in particular their sequence numbers, for
encoding the information.
11. Machine device according to claim 8, being adapted to use
pre-configured network configuration parameters, in particular
pre-configured higher layer parameters, of the radio access network
for communication over the Random Access Channel.
12. Machine network comprising a plurality of machine devices
according to claim 8, the machine network further comprising: a
master machine device adapted to receive network configuration
parameters from the radio access network, and to distribute the
network configuration parameters to the plurality of machine
devices for updating pre-configured network parameters, in
particular higher layer parameters, used in the machine devices for
communication with the radio access network over the Random Access
Channel.
13. Receiving device, in particular base station, for communicating
over a Random Access channel with at least one machine device
according to claim 8, wherein the receiving device is adapted to
decode the information encoded in the pre-selected frequency
offsets between the Random Access Channel preambles transmitted by
the at least one machine device.
14. Receiving device according to claim 13, adapted to identify the
machine device by comparing the decoded information with stored
information about pre-configured frequency offsets of the Radio
Access Channel preambles of a plurality of different machine
devices.
15. System for a radio access network comprising: a base station
for communicating over a Random Access channel with at least one
machine device wherein the base station is adapted to decode the
information encoded in pre-selected frequency offsets between
Random Access Channel preambles transmitted by the at least one
machine device, and a plurality of machine devices, each comprising
a transmission unit adapted for transmitting a plurality of Random
Access Channel preambles over a Random Access Channel to a radio
access network and an encoding unit for encoding information to be
provided to the radio access network over the Random Access
Channel, wherein the encoding unit is adapted to encode the
information by selecting frequency offsets between the Random
Access Channel preambles to be transmitted by the transmission
unit.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the field of telecommunications,
and, more specifically, to methods and devices for performing
Machine Type Communications (MTC) in a radio network.
BACKGROUND
[0002] This section introduces aspects that may be helpful in
facilitating a better understanding of the invention. Accordingly,
the statements of this section are to be read in this light and are
not to be understood as admissions about what is in the prior art
or what is not in the prior art.
[0003] Beside human activated services (e.g. voice and ftp/http
data transfer) in radio communication networks, a new form of
communication, the so called Machine Type Communication (MTC) is
investigated to be integrated into radio communication networks
(such as UMTS, LTE, etc.). However, the design of present radio
communication networks is not preferably designed for machine
devices, e.g. sensors or actuators, acting in MTC. Thus, there are
several challenges to provide an efficient Machine to Machine (M2M)
communication in a settled (legacy) radio network.
[0004] For instance, from the point of view of the machine device,
it is desired to have algorithms that provide energy efficient
working, regarding e.g. limited battery capacity of cheap or small
machine devices such as sensors. The challenge from the network
point of view is how to handle the large number of machine devices
(sensors etc.) spread in a cell of the radio access network. The
objective is not to overload the network, efficiently use Radio
network resources for M2M communications and also not to harm
legacy services (e.g. voice).
SUMMARY
[0005] The present invention is directed to addressing the effects
of one or more of the problems set forth above. The following
presents a simplified summary of the invention in order to provide
a basic understanding of some aspects of the invention. This
summary is not an exhaustive overview of the invention. It is not
intended to identify key or critical elements of the invention or
to delineate the scope of the invention. Its sole purpose is to
present some concepts in a simplified form as a prelude to the more
detailed description that is discussed later.
[0006] One aspect of the invention relates to a method for
providing information from a machine device, in particular from a
sensor device, to a radio access network, the method comprising:
transmitting, by the machine device, a plurality of Random Access
Channel preambles over a Random Access Channel, the information
being encoded by transmitting the Random Access Channel preambles
with pre-selected frequency offsets relative to each other.
[0007] A Random Access Channel (RACH) is generally used by wireless
devices to get the attention of a base station in order to
initially synchronize its transmission with the base station. The
RACH is a shared channel that is used by a plurality of wireless
devices, and the signals (Random Access Channel preambles)
transmitted on the RACH are not scheduled, such that collisions
between RACH preambles of different wireless devices may occur.
[0008] The base stations of radio access networks, e.g. eNB
implementations in LTE, have to recognize data transmitted from
user equipments on the Random Access Channel (RACH) which move with
speeds of up to 500 km/h. The speed of the user equipments leads to
a Doppler shift of the received Random Access Channel preambles of
the RACH which has to be taken into account for decoding.
Therefore, a base station typically has a means for decoding
signals received with a Doppler shift, i.e. with a deviation
(frequency offset) from the nominal frequency of the RACH in the
order of typically several hundred Hz.
[0009] The inventors propose to use the possibility of synchronic
decoding of RACH preambles with different frequencies which is
already available in the base station/radio access network in order
to provide information to the RAN. For this purpose, a plurality of
RACH preambles is transmitted by one and the same machine device,
the information being encoded by using pre-defined frequency
offsets between the RACH preambles which may be recognized by the
base station/radio access network. For instance, a machine-specific
sequence of frequency offsets, or machine-specific frequency
offsets may be chosen for each (or a group of) machine devices,
allowing at least to identify the machine device(s) in the radio
access network based on the pre-selected frequency offsets. The
term "pre-selected" refers to the fact that typically the base
station/RAN has knowledge about the specific frequency
offsets/sequences of frequency offsets of the mobile devices which
may transmit on the RACH. In the way described above, cost and
energy efficient transfer of information from machine devices to
the radio access network/base station may be performed.
[0010] In one variant, the information is also encoded by
transmitting the Random Access Channel preambles with pre-selected
timing offsets relative to each other. In this example, a time
sequence of RACH preambles is transmitted with different frequency
offsets and typically one pre-defined time offset between
subsequent RACH preambles. In this way, a frequency offset hopping
pattern may be provided, using both the time and frequency
dimension to provide information over the RACH to the Radio Access
Network. A specific frequency offset hopping pattern may be defined
for each mobile device, allowing the base station/RAN to identify
the machine device.
[0011] In an alternative variant, at least two, preferably all
Random Access Channel preambles are transmitted at the same point
of time. In this variant, the possibility of synchronic decoding of
several RACH preambles at the same point of time can be
advantageously used for increasing the amount of information which
can be transmitted on the RACH.
[0012] In another variant, the information is also encoded using
the content of the Random Access Channel preambles, in particular
their sequence numbers. By making a selection of the sequence
numbers of the RACH preambles, a further dimension of encoding may
be provided which allows provisioning an additional amount of
information to the radio access network. The selection of the
content of the RACH preambles may be used concurrently with the use
of frequency offsets and possibly also timing offsets, optionally
providing a frequency, time and coding dimension for the
transmitted information.
[0013] In a further variant, at least one of the frequency offsets,
the timing offsets, and the content of the Random Access Channel
preambles is pre-configured in the machine device upon installation
of the machine device. Pre-configuring the machine device with the
frequency offsets and/or RAN specific parameters during
installation is particularly advantageous, as the machine device
need not communicate with the RAN for receiving the pre-defined
frequency offsets. However, especially with machine devices which
move between different locations of the RAN, it may be desirable to
modify/update the pre-selected frequency offsets by explicit
messages from the RAN to the machine devices.
[0014] The proposed idea is most efficient when the speed of the
machine device is known in a receiving device in the RAN. In this
case, the respective Doppler shift (frequency offset) of the
received radio signal is known beforehand and can be used as a
basis for the first point of the proposed frequency offset (and
possibly time offset) hopping pattern.
[0015] In another variant, the encoded information comprises
identification information for identifying the machine device
and/or status information for informing the radio access network
about a status of the machine device. When the machine device is a
sensor device which only observes if a single quantity, e.g.
temperature, stress, etc. is in a pre-defined range, a RACH
preamble sequence may only be sent by the sensor device as soon as
the measured quantity is out of the specific range. In this case,
the transmission of the RACH preambles by the sensor device is
already a status information indicating that there is a problem
with the quantity being observed by the sensor device.
[0016] In a further variant, the Random Access Channel preambles
are transmitted using a power level which is selected based on a
power level of a previous successful communication between the
machine device and the radio access network over the Random Access
Channel. As indicated above, the RAN connection is guaranteed
through the RACH procedure (random access), using uplink
transmissions with increasing power levels. Thus, the RACH
procedure may have different power ramp up steps until a successful
set-up of the RACH procedure is achieved, i.e. the RAN is capable
of decoding the RACH preamble(s).
[0017] The last power ramp up level of a successful RACH procedure
may be stored in the machine device. For the next network RACH
procedure, either the stored power ramp up level or e.g. the power
ramp up level one step below the stored level may be used, thus
reducing the number of steps and consequently the power consumption
of the RACH procedure. This approach is most efficient if used for
stationary (non-mobility) sensors (e.g. sensors attached to a
bridge or at defined traffic points for reporting traffic,
etc.)
[0018] A further aspect of the invention relates to a (machine)
device, in particular to a sensor device, comprising: a
transmission unit adapted for transmitting a plurality of Random
Access Channel preambles over a Random Access Channel to a radio
access network, and an encoding unit for encoding information to be
provided to the radio access network over the Random Access
Channel, the encoding unit being adapted to encode the information
by (pre-)selecting frequency offsets between the Random Access
Channel preambles to be transmitted by the transmission unit.
[0019] One skilled in the art will appreciate that although
typically the (machine) device typically provides low
functionality, is cheap and should not consume much energy, other
devices, e.g. wireless mobile terminals used for interaction with
users (user equipments), may be provided with the additional
functionality to use the Random Access Channel for the transfer of
information to the RAN.
[0020] In one embodiment, the encoding unit is further adapted to
select timing offsets between the Random Access Channel preambles
for encoding the information. In addition to the frequency offsets,
timing offsets may be provided between the RACH preambles, allowing
to use a time and frequency pattern for transmitting the
information to the RAN. Although the same timing offset may be used
for all preambles of the RACH preamble sequence, it may also be
possible to modify the timing offset between subsequent preambles
of the sequence, providing an additional degree of freedom for the
encoding.
[0021] In another embodiment, the encoding unit is further adapted
to select the content of the Random Access Channel preambles, in
particular their sequence numbers, for encoding the information.
The information to be provided may also be encoded using the
content of the RACH preambles. By using this additional degree of
freedom for the encoding, the number of RACH preambles required for
transmitting a specific amount of information may be reduced,
avoiding to overload the Random Access Channel by efficient use of
Radio network resources.
[0022] In another embodiment, the machine device is adapted to use
pre-configured network configuration parameters, in particular
pre-configured higher layer parameters, of the radio access network
for communication over the Random Access Channel. For an energy
efficient sensor node implementation, a network pre-configuration
may be uploaded on site during the first setup (installation) of
the sensor in the field. For this purpose, higher layer parameters,
i.e. parameters from layers above the physical layer, such as
network and cell specific layer 2 and layer 3 parameters, are read
from system information of the RAN and are uploaded to the machine
device, typically during installation of the machine device (in the
field). Layer 2 and layer 3 procedure parameters may then be stored
in the machine device and may either be used for its entire
life-time or until the next update period (e.g. in case of a
relevant network parameter change). In this way, there is no need
for a complete layer 2 and layer 3 hardware and/or software
integration in the machine device.
[0023] A further aspect relates to a machine network comprising a
plurality of machine devices of the type described above, the
machine network further comprising: a master machine device adapted
to receive network configuration parameters from the radio access
network, and to distribute the network configuration parameters to
the plurality of machine devices for updating pre-configured
network parameters, in particular higher layer parameters, used in
the machine devices for communication with the radio access network
over the Random Access Channel. Such a machine network is
particularly advantageous in order to avoid power-consuming
wireless communications of the machine devices with the RAN.
[0024] In the machine network, the master machine device is used
for receiving the network configuration parameters from the radio
access network and to distribute the parameters to the other
machine devices, which may be connected to the master machine
device e.g. via cabling or possibly using short-range wireless
communications such as ZigBee, Bluetooth, etc. having comparatively
low power consumption.
[0025] Yet another aspect relates to a receiving device, in
particular to base station, for communicating over a Random Access
channel with at least one machine device as described above, the
receiving device being adapted to decode the information encoded in
the frequency offsets and preferably in the timing offsets between
the Random Access Channel preambles and/or the contents of the
Random Access Channel preambles transmitted by the at least one
machine device. Using the receiving device, based on the decoded
information, a specific machine device may be identified and
additional information, e.g. about the status of the machine
device, may be obtained by the RAN.
[0026] In one embodiment, the receiving device is adapted to
identify the machine device by comparing the decoded information
with stored information about pre-configured frequency offsets and
preferably pre-configured timing offsets between the Radio Access
Channel preambles and/or the contents of the Radio Access Channel
preambles transmitted by a plurality of different machine
devices.
[0027] When using e.g. a time and frequency coding, a grid with
fixed frequency and timing offsets for the RACH preambles of all
the machine devices may be defined in the RAN. For each machine
device, a pre-selected, preferably unique selection of points in
the time/frequency grid (frequency hopping pattern) may be chosen
and stored in the receiving device or elsewhere in the RAN.
[0028] Another aspect of the invention relates to a cell for a
radio access network, comprising: a receiving device in the form of
a base station as indicated above, and a plurality of machine
devices of the type described above. The cell may be part of a RAN
which provides M2M communication over the RACH. The pre-requisite
for performing the communications is that the RAN provides the
possibility to decode signals in a frequency range which allows
taking the Doppler shift into account, which is the case e.g. with
the LTE (advanced) standard, or other standards which provide this
possibility.
[0029] Further features and advantages are stated in the following
description of exemplary embodiments, with reference to the figures
of the drawing, which shows significant details, and are defined by
the claims. The individual features can be implemented individually
by themselves, or several of them can be implemented in any desired
combination.
BRIEF DESCRIPTION OF THE FIGURES
[0030] Exemplary embodiments are shown in the diagrammatic drawing
and are explained in the description below. The following are
shown:
[0031] FIG. 1 shows a schematic diagram of a cell according to the
invention, providing M2M communications over a RACH channel for a
plurality of sensor devices,
[0032] FIGS. 2a,b show time/frequency diagrams for two different
ways of transmitting a plurality of RACH preambles by one of the
sensor devices of FIG. 1, and
[0033] FIG. 3 shows a schematic representation of a machine network
according to the invention.
DESCRIPTION OF THE EMBODIMENTS
[0034] The functions of the various elements shown in the Figures,
including any functional blocks labeled as `processors`, may be
provided through the use of dedicated hardware as well as hardware
capable of executing software in association with appropriate
software. When provided by a processor, the functions may be
provided by a single dedicated processor, by a single shared
processor, or by a plurality of individual processors, some of
which may be shared. Moreover, explicit use of the term `processor`
or `controller` should not be construed to refer exclusively to
hardware capable of executing software, and may implicitly include,
without limitation, digital signal processor (DSP) hardware,
network processor, application specific integrated circuit (ASIC),
field programmable gate array (FPGA), read only memory (ROM) for
storing software, random access memory (RAM), and non volatile
storage. Other hardware, conventional and/or custom, may also be
included. Similarly, any switches shown in the Figures are
conceptual only. Their function may be carried out through the
operation of program logic, through dedicated logic, through the
interaction of program control and dedicated logic, or even
manually, the particular technique being selectable by the
implementer as more specifically understood from the context.
[0035] FIG. 1 shows a radio access network RAN according to the LTE
(advanced) standard which has a plurality of cells, only one of
which (cell C) being shown for the sake of simplicity. The cell C
comprises a base station BS and serves a plurality of machine
devices in the form of sensor devices S1 to Sn not supporting human
activated services, as well as user equipments supporting such
services only one of which (user equipment UE) is represented in
FIG. 1. The sensor devices S1 to Sn as well as the user equipments
UE perform communications over a Random Access Channel RACH to get
the attention of the base station BS in order to initially
synchronize their transmissions with the base station BS.
[0036] In the present example, the Random Access Channel RACH is
also used for providing information from specific ones of the
sensor devices S1 to Sn to the base station BS. For this purpose, a
sensor device, e.g. the first sensor device S1, transmits a
plurality of RACH preambles P1 to P3 over the Random Access Channel
RACH, as indicated in FIGS. 2a,b, the information being encoded in
the specific way in which the transmission of the RACH preambles P1
to P3 is performed, as will be outlined below.
[0037] In the example shown in FIG. 2a, three RACH preambles P1 to
P3 are transmitted subsequently at time instances t0 to t3 by the
first sensor device S1, a (constant) timing offset .DELTA.t/time
interval being provided between subsequent ones of the time
instances t0 to t3. Moreover, the RACH preambles P1 to P3 are
transmitted using frequency offsets +.DELTA.f, -.DELTA.f etc. with
respect to each other. In the present example, the sensor device S1
is stationary and provides the first RACH preamble P1 with a
frequency which does not deviate from a nominal frequency of the
RACH channel, represented as 0 Hz in FIG. 2a.
[0038] The second preamble P2 is transmitted with a positive
frequency offset of .DELTA.f=+1000 Hz with respect to the nominal
frequency, whereas the third preamble P3 is transmitted with a
negative frequency offset of .DELTA.f=-1000 Hz with respect to the
nominal frequency of the Random Access Channel RACH.
[0039] In the present example, an identical spacing for the time
and frequency offsets is chosen for all of the sensor devices S1 to
Sn, defining a two-dimensional grid in which specific points in
frequency and time (frequency hopping pattern) are defined for each
sensor device S1 to Sn, providing an individual signature allowing
to identify a specific one of the sensor devices S1 to Sn in a
unique way.
[0040] In the example of FIG. 2a, identification of a the first
sensor device S1 is provided by identifying its (unique) signature
of the three subsequent frequency offsets with values 0, +1, -1,
transmitted at respective times t.sub.0, t.sub.1, and t.sub.2. It
will be understood that FIG. 2a shows only a simple example of a
time/frequency grid and that both the number of different frequency
offsets and the number of subsequent transmissions of RACH
preambles may be higher or lower than those indicated in FIG. 2a.
In a similar manner, the second sensor device S2 may be identified
by a sequence of frequency offsets being e.g. 0, -1, +1, etc.
[0041] FIG. 2a also shows a power level p of the uplink RACH
preambles P1 to P3. During the RACH procedure, different (discrete)
power ramp up steps may have to be performed until a power level is
reached which allows successful communication with the RAN. The
last power ramp up level, i.e. the power level which allows a
successful RACH procedure, is stored in the sensor device S1. In a
subsequent RACH procedure, either the stored power level may be
used as a first ramp up level, or a power level just below the
stored power level may be used as first power level of the
subsequent RACH procedure. In this way, the power consumption of
the RACH procedure may be reduced, as a smaller number of power
ramp up steps will be required.
[0042] Instead of using a sequence of RACH preambles P1 to P3
transmitted at different points of time, it is also possible to
transmit all or at least some of the RACH preambles P1 to P3 at the
same instant of time t0, as indicated in FIG. 2b. Typically, when
this option is used, a relatively high number of different
frequency levels is required for encoding the information. In order
to reduce the number of frequency levels, the information to be
provided to the Random Access Network RAN can additionally be
encoded by selecting a specific RACH preamble content, in the
present case a sequence number C.sub.0, C.sub.1, C.sub.2. In this
way, the three RACH preambles P1 to P3 can be differentiated by
their content, as indicated in FIG. 2b (for a simple graphical
representation only) by three different amplitudes of the RACH
preambles P1 to P3, and identification of a specific sensor device
S1 is possible in the RAN by comparing the signature of the
sequence numbers C.sub.0=2, C.sub.1=1, and C.sub.2=3 with
pre-defined signatures of a plurality of sensor devices S1 to
Sn.
[0043] As indicated above, it is also possible to combine the
coding of FIG. 2b with that of FIG. 2a, i.e. to combine frequency
coding with time and/or with content coding. In any case, the
different frequencies of the RACH preambles P1 to P3 have to be
decoded by the base station BS, which is implemented as an eNB in
the present example of a Radio Access Network RAN in compliance
with the LTE standard. As the base station BS has the capability to
decode signals transmitted on the RACH which deviate from the
nominal frequency of the RACH by an offset due to a Doppler shift
which may be e.g. in the order of +/-1000 Hz or more, the base
station BS may be used to decode the information as a signature
within a grid of frequency offsets having an equal spacing and
ranging e.g. from -3.DELTA.f, -2 .DELTA.f, -.DELTA.f to +.DELTA.f,
+2 .DELTA.f, +3+.DELTA.f, etc. In addition, the base station BS is
also capable to determine the content of the RACH preambles P1 to
P3, and to correlate the content of the RACH preambles with the
specific time instant and frequency at which it is received.
[0044] As it is mandatory for the base station BS to first identify
a particular sensor device S1 to Sn before it can make use of
status information which is provided by that sensor device S1 to
Sn, the base station BS compares the specific frequency, time
and/or content of the received RACH preambles with stored
information about pre-configured frequency offsets and possibly
pre-configured timing offsets and content which is used as a
signature (coding) allowing to identify a specific one of the
sensor devices.
[0045] Although in the above description it has been proposed to
use the same spacing of frequency offsets for all sensor devices S1
to Sn, it may also be possible to differentiate the sensor devices
S1 to Sn by selecting a specific frequency spacing and/or time
spacing (i.e. a specific time/frequency grid) for each sensor
device S1 to Sn which allows to identify that specific sensor
device S1 to Sn. In this case, the signature/pattern which is
provided in the sensor-specific grid can be used entirely to
provide status information to the RAN. Alternatively, for
transmitting sensor-specific status information, the sensor devices
S1 to Sn may be identified e.g. by pre-defined number of RACH
preambles which are the first ones in a transmitted sequence, the
remaining RACH preambles of the sequence being used for the
providing status information about the specific sensor device S1 to
Sn to the Radio Access Network RAN. It will be understood that
alternatively, the mere transmission of a RACH sequence may be
sufficient to indicate that something is wrong with the
component/machine which is monitored by that specific sensor
device. In particular, the sensor device may only transmit a RACH
preamble when a quantity measured by the sensor device, e.g. a
temperature, deviates from a targeted range.
[0046] Furthermore, for an energy efficient sensor implementation,
a network pre-configuration may be uploaded on site during the
first setup of the sensor devices S1 to Sn, i.e. an operator may
store pre-configured network-specific parameters of the higher
layers (above the physical layer) of the radio network, resp., of
the cell C which serves the sensor devices S1 to Sn, when
installing the sensor devices S1 to Sn in the field.
[0047] The higher-layer network parameters may be stored in the
sensor devices S1 to Sn during their entire lifetime (especially in
the case of static sensor devices), or, alternatively, the higher
layer parameters may be updated regularly or when a sensor-relevant
network parameter change occurs. In this way, a complete hardware
and/or software integration of the higher network layers in the
sensor devices S1 to Sn can be dispensed with.
[0048] In particular, an update or initialization of the sensor
devices S1 to Sn may be performed in a way which will be explained
now with reference to FIG. 3, showing a machine network MN
comprising a master sensor device MS which is adapted to receive
current network configuration parameters LP2, LP3 of the second and
third layer of the LTE standard from the radio access network RAN
(see FIG. 1), and is further adapted to distribute the network
configuration parameters LP2, LP3 to the plurality of sensor
devices S1 to Sn for updating pre-configured semi-static network
parameters LP2.sub.s, LP3.sub.s currently stored in the (slave)
sensor devices S1 to Sn.
[0049] The sensor devices S1 to Sn will then update the sensor
parameters LP2.sub.s, LP3.sub.s, i.e. they will replace them with
the values LP2, LP3 currently received from the master device MS.
The advantage of the configuration of FIG. 3 is that the sensor
devices S1 to Sn and the master sensor device MS may use a specific
sensor interface for the communication, which may be wire-based
(via cabling) or wireless, typically using a short-range wireless
communication standard, e.g. a ZigBee standard, thus reducing the
power consumption for the communications. It will be understood
that the RACH preambles may also be sent from the sensor devices S1
to Sn via the master sensor device MS to the RAN.
[0050] Of course, the sensor devices S1 to Sn of the machine
network MN may also provide the RACH preambles P1 to P3 directly to
the RAN. For this purpose, an exemplary sensor device Sn shown in
FIG. 3 comprises a transmission unit TU for wireless communications
with the RAN over the Random Access Channel RACH. In addition, the
sensor device Sn also comprises an encoding unit EU for encoding
information to be provided to the radio access network RAN over the
Random Access Channel RACH, the encoding unit EU being adapted to
encode the information in the way described with reference to FIGS.
2a,b above, i.e. using specific patterns in the frequency, and
possibly in the time and/or code/content domain.
[0051] In the way described above, the communication of the
(access) network with a large number (e.g. several hundreds) of
sensors spread in a cell may be handled in a way which does not
overload the network, and makes efficient use of radio network
resources for M2M communications, such that legacy services (e.g.
voice) will not suffer from the additional communications with the
sensor devices.
[0052] Those skilled in the art will appreciate that the transfer
of encoded information to the Radio Access Network RAN over the
Random Access Channel RACH is not limited to sensor devices. In
particular, user equipments UE (see FIG. 1) which allow human
interactions may also be provided with this additional
communication functionality.
[0053] Moreover, it will be appreciated that although the above
description has been given with respect to a radio access network
in compliance with the LTE (advanced) standard, it may be applied
equally well to radio networks using a Random Access Channel and
which allow decoding of signals in the Random Access Channel within
a certain frequency range deviating from a nominal frequency in
order to take Doppler shifts into account.
[0054] It should be appreciated by those skilled in the art that
any block diagrams herein represent conceptual views of
illustrative circuitry embodying the principles of the invention.
Similarly, it will be appreciated that any flow charts, flow
diagrams, state transition diagrams, pseudo code, and the like
represent various processes which may be substantially represented
in computer readable medium and so executed by a computer or
processor, whether or not such computer or processor is explicitly
shown.
[0055] Also, the description and drawings merely illustrate the
principles of the invention. It will thus be appreciated that those
skilled in the art will be able to devise various arrangements
that, although not explicitly described or shown herein, embody the
principles of the invention and are included within its scope.
Furthermore, all examples recited herein are principally intended
expressly to be only for pedagogical purposes to aid the reader in
understanding the principles of the invention and the concepts
contributed by the inventor(s) to furthering the art, and are to be
construed as being without limitation to such specifically recited
examples and conditions. Moreover, all statements herein reciting
principles, aspects, and embodiments of the invention, as well as
specific examples thereof, are intended to encompass equivalents
thereof.
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